The present invention relates to the field of hydrocarbon purification. In another aspect, the invention relates to a method for regenerating a purification system suitable for removing water and heteroatom-containing compounds from hydrocarbons.
The presence of water and/or heteroatom-containing compounds can pose a problem in various hydrocarbon conversion processes. Included among these processes is the alkylation of olefins with saturated hydrocarbons, such as isoparaffins, by contacting the reactants with an acid catalyst to form a reaction mixture, settling the reaction mixture to separate the catalyst from the hydrocarbons and further separating the alkylation reactor effluent to recover the separate product streams. In typical alkylation units, the unreacted isoparaffin and olefin feeds are recycled to the alkylation reactor for recontact with the acid catalyst. An undesirable result of such recycle is the buildup of water and/or heteroatom-containing compounds in the isoparaffin and olefin streams.
The presence of water and/or heteroatom-containing compounds in the olefin or isoparaffin streams can cause lower alkylate octane and phase separation problems in the acid recovery section of the alkylation unit.
Therefore, development of a more efficient process for regenerating a hydrocarbon purification system suitable for removing water and heteroatom-containing compounds from hydrocarbons would be a significant contribution to the art and to the economy.
It is, thus, an object of the present invention to provide an improved method/system for regenerating a hydrocarbon purification system suitable for removing water and/or a heteroatom-containing compound from a hydrocarbon stream, which is economical in construction and efficient in operation.
A further object of the present invention is to provide a method of treating a hydrocarbon stream containing at least one heteroatom-containing compound and water using a purification system, wherein the method includes an improved method for regenerating the purification system by removing accumulated water and heteroatom-containing compound.
In accordance with the present invention, a method of regenerating a hydrocarbon purification system is provided and includes the steps of:
(a) introducing a stripping stream comprising an isoparaffin into the contacting zone of a treatment system containing (1) a water adsorbent containing water, and (2) a heteroatom-containing compound adsorbent containing a heteroatom-containing compound; such that the stripping stream contacts the water adsorbent prior to contacting the heteroatom-containing compound adsorbent;
(b) withdrawing a spent stripping stream comprising isoparaffin, heteroatom-containing compound and water from the contacting zone; and, optionally, further including the steps of:
(c) cooling the spent stripping stream to form a cooled spent stripping stream;
(d) introducing the cooled spent stripping stream to a settler for separation into a hydrocarbon phase and a water phase;
(e) removing a portion of the hydrocarbon phase from the settler to form a circulating hydrocarbon stream;
(f) mixing the circulating hydrocarbon stream with water to form a hydrocarbon/water mixture;
(g) introducing the hydrocarbon/water mixture to the settler for separation into the hydrocarbon phase and the water phase;
(h) removing a portion of the hydrocarbon phase from the settler to form a recycle isoparaffin stream, wherein the recycle isoparaffin stream contains less water and less heteroatom-containing compound as compared to the cooled spent stripping stream; and
(i) using at least a portion of the recycle isoparaffin stream as at least a portion of the stripping stream.
Other objects and advantages of the invention will be apparent from the detailed description of the invention and the appended claims.